Containers, and more specifically metallic beverage containers, are typically manufactured by interconnecting a beverage can end closure on a beverage container body. In some applications, an end closure may be interconnected on both a top side and a bottom side of a can body. More frequently, however, a beverage can end closure is interconnected on a top end of a beverage can body which is drawn and ironed from a flat sheet of blank material such as aluminum. Due to the potentially high internal pressures generated by carbonated beverages, both the beverage can body and the beverage can end closure are typically required to sustain internal pressures exceeding 90 psi without catastrophic and permanent deformation. Further, depending on various environmental conditions such as heat, over fill, high CO2 content, and vibration, the internal pressure in a typical beverage can may at times exceed 100 psi. Thus, beverage can bodies and end closures must be durable to withstand high internal pressures, yet manufactured with extremely thin and durable materials such as aluminum to decrease the overall cost of the manufacturing process and the weight of the finished product.
Accordingly, there exists a significant need for a durable beverage container end closure which can withstand the high internal pressures created by carbonated beverages, and the external forces applied during shipping, yet which is made from a durable, lightweight and extremely thin metallic material with a geometric configuration which reduces material requirements. Previous attempts have been made to provide beverage container end closures with unique geometric configurations to provide material savings and improve strength. One example of such an end closure is described in U.S. Pat. No. 6,065,634 To Crown Cork and Seal Technology Corporation, entitled “Can End and Method for Fixing the Same to a Can Body”. Other inventions known in the art have attempted to improve the strength of container end closures and save material costs by improving the geometry of the countersink region. Examples of these patents are U.S. Pat. Nos. 5,685,189 and 6,460,723 to Nguyen et al, which are incorporated herein in their entirety by reference. Another pending application which discloses other improved end closure geometry is disclosed in pending U.S. patent application Ser. No. 10/340,535, which was filed on Jan. 10, 2003 and is further incorporated herein in its entirety by reference. Finally, the assignee of the present application owns another pending application related to reforming and reprofiling a container bottom, which is disclosed in pending U.S. patent Ser. No. 11/020,944 and which is further incorporated herein by reference in its entirety.
The following disclosure describes an improved container end closure which is adapted for interconnection to a container body and which has an improved countersink, chuck wall geometry, and unit depth which significantly saves material costs, yet can withstand significant internal pressures.
Previous methods and apparatus used to increase the strength of a container end closure have generally been attempted using traditional forming presses, which utilize a sequence of tooling operations in a reciprocating press to create a specific geometry. Unfortunately with the use of small gauge aluminum and other thin metallic materials, it has become increasingly difficult to form a preferred geometry without quality control issues as a result of the physical properties of the end closure and the difficulty of retaining a desired shape. Furthermore, when a thin metallic material is worked in a traditional forming press, certain portions of the end closure may be thinned, either from stretching, bending operations, commonly known as “coining”. When excessive thinning occurs, the overall strength and integrity of the end closure may be compromised. Further, it is practically impossible to form certain geometries with a typical die press. Thus, there is a significant need in the industry for a new method and apparatus for forming a preferred shape in an end closure, and which uses rollers and other mechanical devices which can form a preferred shape in the end closure without requiring traditional forming presses and the inherent problems related thereto.
Furthermore, new end closure geometries are needed which have distinct shapes and provide superior strength and buckle resistance when interconnected to pressurized containers. As previously mentioned these geometries are typically not feasible using traditional end closure manufacturing techniques. Thus, there is a significant need for new end closure geometries which have improved strength characteristics and which are capable of being formed with thin walled metallic materials.